So, let's say there's only 2,000,000 people and there are 5,000 portapotties. Unless my math is wrong that one john for every 2,000 people. Wikipedia Answers suggest a ratio of 1 to 50; other sites suggest 1 to 15, especially when there are children. Even opening the toilets in the various museums and things still wouldn't affect the ratio much.

AND I'm being very conservative here.

Looks like there will be a LOT of "other cleaning up" to do....